Let me expand the answer for those (you) who need it.
Makers, even the better known ones like Colt, outsource many AR small parts.
50 miles from my house is a plant that used to be one of TWO lower receiver manufacturers for a name brand located 2000 miles away that I won't mention. The contract buyer would then do their own stamping when they built the guns in their own plant.
Makers simply don't build every part themselves in an AR.
Depending on who & what, they may buy in bulk from a parts vendor to generic specs, or contract with the small parts maker for their own specs.
You don't know who made what on ANY AR right down to the last pin, and there's no such thing as "authentic" to RR or any other maker across the board as far as parts go.
RR may make some or may make many of their own parts, but there are very few makers who label parts such as bolts, carriers, and so on. BCM is one exception I'm aware of.
Even a maker's stamp on an AR part does not guarantee that maker actually made it.
Your upper could exist now as it came from the RR factory, or it could contain replacement parts.
In many of those, there is no way to confirm by looking at them.
In some, I doubt even RR couldn tell you.